1. Field of the Invention
The present invention generally relates to micro isolation cages for animals. More particularly, the invention relates to a flask containing water or other liquid for feeding laboratory animals in the cage. Still more particularly, the invention relates to a water flask located substantially outside the living area of the animals and having a water level that is easily viewed.
2. Background of the Invention
Research laboratories all over the world commonly use animals to conduct medical research experiments. The use of mice, for example, as test subjects in medical research has made possible the cure of many diseases. As is true for any experiment, it is important to carefully control the variables that may effect the test results involving laboratory mice. For instance, it is necessary to ensure that each test mouse does not become contaminated by other animals or people in the laboratory. For simplicity in explaining the preferred embodiments of the invention, this disclosure focuses on mice, but the invention applies broadly to other types of animals such as rats.
To minimize the potential for contaminating the animals, as well as to insure a comfortable, safe, and clean living environment, the mice are housed in micro isolation cages. High efficiency air filters, such as High Efficiency Particulate Air (HEPA) filters, may be incorporated into a ventilation system connected to the cages to reduce the level of airborne contaminants, and reduce levels of gaseous contamination produced by animal metabolism. Such ventilation systems often are designed to provide positive air pressure to the living space of the mice relative to ambient pressure in the laboratory to help further prevent airborne contaminants from detrimentally effecting the mice.
Large research laboratories may include hundreds of cages to facilitate testing on a large number of animals. FIG. 1 shows an exemplary configuration of a rack 32 containing nine shelves of mice cages 34. Each shelf has room for seven cages and thus the rack has a total of 63 mouse cages. Many racks are double-sided providing room for 63 cages on a side, or 126 total cages in the rack. Each cage has sufficient room for as many up to 5 mice to live comfortably. Many research laboratories have many such racks containing tens or even hundreds of thousands of mice.
Part of the nutrition provided to the mice includes water. Conventional micro isolation cages include water bottles resting on a wire bar lid inside the cage top. The mice are able to lick water from a sipper tube connected to the water bottle. The water bottle is located inside the cage because that is where the mice are located. Typically, conventional water bottles are large enough to hold enough water for about one week in a cage containing 5 adult mice. Once empty, the water bottle must be refilled or replaced by a technician.
Filling or replacing the water bottles is a time consuming, expensive task. Because the water bottles are located inside the cage, the cage must be opened to access the water bottle. To minimize the potential for contamination of the mice when the lid is opened, a laboratory technician must remove the cage from the rack and place the cage in a specially designed, laminar air flow workstation when changing the water bottle. Such workstations typically include HEPA filters and other specialized components to reduce the potential for contaminating the mice. The process of removing the cage from the rack, placing it in a work station, changing the water bottle, and placing the cage back in the rack is a time consuming activity for a single cage. That amount of laboratory technician time multiplied by the large number of cages in many research laboratories results in a significant labor cost just to replace water bottles in all of the cages.
Because of the relatively large number of micro isolation cages required, the special requirements associated with each cage, the specially designed rack units required to house the cages, and the special air circulation equipment required, mice containment facilities typically result in a significantly large capital investment. Any improvements or other alterations made to the equipment should be made taking cost into account.
It thus would be desirable to reduce the labor cost. One way to reduce this cost is provide a water bottle with a larger volume permitting the bottle to contain more water than conventional water bottles. A water bottle that can hold enough water for a two week time period, for example, would be highly desirable. The time spent on replacing water bottles would be reduced significantly because the bottles could be changed less often than with smaller, conventional bottles. The time spent to change an individual bottle, however, would be the same as with conventional bottles because the cage still would have to be placed in a workstation to prevent contamination of the mice when the lid is removed to access the larger water bottle.
Simply increasing the dimension of a conventional water bottle is problematic. Because conventional water bottles are located inside the isolation cage, a larger bottle would encroach on the living area of the mice and/or the space used to provide food to the animals. Thus, a design for a larger water bottle should minimize the encroachment into the animals' living space.
Another problem with conventional water bottles is that the level of water in the bottle is often difficult to view without taking the cage out of the rack. Typically, isolation cages are located in close proximity to one another and thus it is difficult to see the water bottle in each cage without at least partially removing the cage from the rack. It thus would be desirable to provide a water bottle for a micro isolation cage that provides an indication of water level that is easy to view without having to remove the cage.
Not only can labor cost be reduced by providing a larger water supply for each cage, but labor cost can also be reduced by providing a larger food supply. With a larger supply of food, a laboratory technician is able to add more food to the cage on a less frequent basis. The solution to the problem of how to provide a larger water and food supply also should take into account the desirability of having as many cages as possible in a given rack without substantially reducing the available living space for the mice in each cage. More specifically, it would be desirable to have at least the same number of cages provided in isolation cage and rack designs but with each cage having a larger supply of water. For example, it would be desirable to still have at least 63 cages on each side in a rack as shown in the exemplary rack design of FIG. 1. Accordingly, each cage and water bottle assembly should encompass a total volumetric envelope approximately the same as that of conventional isolation cages.
Accordingly, a water bottle for a micro isolation cage that solves the problems noted above would be beneficial. It would be particularly beneficial to provide an improved water bottle arrangement that permits the use of as much existing cage and rack equipment as possible, thus minimizing the cost impact in using the improved water bottles. Further, such a bottle should provide a water level indicator that is easy to read without taking the cage out of the rack. Also, it would be desirable to change the water bottle without having to incur the labor time and cost of placing the entire cage in a work station. Despite the advantages that such a water bottle and isolation cage system would offer, to date no such system has been introduced.